Signaling system for single-track railroads



I INVENTOR. ReedBAnneaP 2 SHEETS--SHEET 1 H15 ATTORNEY R. B. ANNEARSIGNALING SYSTEM FOR SINGLE-TRACK RAILROADS NEE D xxfigm W1 m Jan. 8,1952 Filed Jan. 25, 1949 2 SHEETS-SHEET 2 V kw m 1 Q Q n b JNVENTOR.

BY i i) HIS ATTORNEY HM m3 QYT w www mmwww m 14 1 NI gh wmma ML- J n E14 1+ .& \w

Nam nm @RES wa R. B. ANNEAR SIGNALING SYSTEM FOR SINGLE-TRACK RAILROADSNT. Q vhku x mm F 5 3 4 dm nwwwv \fimkw r MES YMUIII wax QRSE H m 1% PH5% Jan. 8, 1952 Filed Jan. 25, 1949 Patented Jan. 8, 1952 SIGNALINGSYSTEM FOR SINGLE-TRACK RAILROADS Reed B. Annear, Omaha, Nebr., assignorto Westinghouse Air Brake Company, a corporation of PennsylvaniaApplication January 25, 1949, Serial No. 72,568

My, invention relates to signaling systems for single track railroads,and more particularly, to single track signaling systems of the normallyinactive reversible coded track circuit type such as the one shown anddescribed in reissue patent of. the United States, No. 22,780, reissuedAugust 13, 1946, to J. J. Van Horn, for Railway Traffic ControllingApparatus, which system is also described in an article on pages 423-431of the August 1944 issue of the magazine Railway Signaling, published:by the Simmon Boardman Publishing Corporation of Chicago, Illinois.

In signaling systems of this character, continuous track circuits areprovided for all main track, and a centralized trafiic control system isemployed to enable the reversible track circuit system for the singletrack stretches between passing sidings to be set up for eitherdirection of traffic movement and to enable the head block signals whichgovern movements into the single track blocks, as well as the enteringsignals which govern traflic movements into the passing tracks at theends of the blocks, to be manually controlled from a central ofiice.

A characteristic of the Van Horn system is that the track circuits forthe successive sections of a block have track relays and batteries atboth ends, and normally a battery is connected to the rails at theentrance end of the block, for the traffic direction established, andthe track relays at the exit ends of the sections are energized incascade, the track relay at the exit end of the last block sectioncontrolling an indicator at the oflice to indicate that the entire"block is vacant. Under this condition the operator is enabled toreverse the traffic direction by energizing a traffic control relay atone end and releasing a similar trafiic control relay at the otherend ofthe block by remote control, thereby disconnecting the battery at theone a block end and connecting a battery to the rails at the other blockend whereupon the track relays at the opposite ends of the sectionsbecome energized in cascade. The system thus is normally in an inactiveconditionin which all of the track circuits are energized by steadycurrent in a direction corresponding to that established for trafficmovements, which direction is theopposite to that required. for thecontrol ,of, the signals governing such movements.

To place the system;in-itsactive'condition and to clear the head block,signal whi'ch governs trafiic movements into the block in the established direction, the operator at the control 5 Claims. (01. 246--3)trol relay at the entrance end of the block, and this relay prepares acircuit for the associated signal and also disconnects the adjacentbattery from the track rails. The resulting deenergization of thecascade connected track circuit system in this case has the effect ofpreventing a subsequent reversal in the traiiic direction, and inaddition, causes coded current interrupted periodically at the rate ofor times per minute to be supplied to the rails at the exit end of theblock for signal control purposes, and the track circuits then becomeenergized in cascadeby coded current, to clear the head block signalhaving its control relay energized. When a train governed by that signalenters the block, its signal control relay releases and automaticallyrestores the system to the inactive condition above described.

In addition to the manually controlled head block signals referred to,the system also includes intermediate signals at spaced locations in thesingle track block such as those shown in Fig. 1c of the Van Hornpatent, which signals are governed automatically to indicate caution orproceed in accordance with traffic conditions, when 75 or 180 codedcurrent is received over the track rails of the block section inadvance, and also govern the supply of such current to the rails of thesection in the rear.

Conventionally, 75 code is supplied to the rails at the exit end of theblock when the signal which governs train movements out of the singletrack stretch is at stop, and 180 code is supplied when that signalindicates caution or proceed. At each intermediate signal location, '75code is supplied to the rails of the section in the rear of the signalwhich governs train movements in the established direction when theadvance section is occupied, and 180 code is supplied to therails of therear section when 75 or 180 code is received from the rails of theadvance section.

My invention relates to the control of intermediate signals in a systemof this character in a situation where the single track block is soshort that the conventional arrangement shown in Fig. 1c of the Van Hornpatent is not applicable andit is necessary to stagger the signallocations and to overlap the control limits for the intermediatesignal'sfand also those for the signals in approach thereto in order toprovide adequate stopping distances for high speed trains.

More specifically, the principal object of my ines, by mnqtecgnnotcng eia signal con- 56 inven on s t i i e mp co t i i location E and replacingit by one at location F, without shortening the control limits for thewestbound approach signal in the rear thereon,

such as signal IDLA in Van Horns Fig. 1d, and j by extending the controllimits for the eastbound signal in the rear of signal IE through point Eto point F.

My invention is applicable to any stretch of railway track equipped witha-coded track circuit signaling system of the type referred to,, whichis divided into three track sections arranged to provide two overlappingblock sections having a common portion comprising the intermediate tracksection of the stretch, with intermediate signals at the opposite endsof the intermediate track section and approach signals at the. end ofthe stretch each governed in accordance with trafiic conditions in theblock section in advance of the signal.

Heretofore in a situation of this kind it has been necessary to providea complete set of traffic and signal control apparatus for a pair ofopposing intermediate signals such as is shown in Van Horns Fig. 10, ateach intermediate signal location even though there is only one signalat such location.

My invention enables the amount of apparatus required to be materiallyreduced, and as in the Van Horn patent, I provide a complete setoftraffic and signal control apparatus at the location of the firstintermediate signal only, and at the location of the second intermediatesignal I also provide cut-section apparatus to enable the intermediatetrack section and the second end section to function as a single blocksection for the control of the first intermediate signal and of theapproach signal in the rear of the second intermediate signal, attheopposite end of the same block section.

In accordance with a feature of my invention, this second intermediatesignal is controlled over a line circuit governed by traffic conditionsinthe intermediate section and first end section, and means are providedfor preventing the clearing of the approach signal in the rear of thesecond intermediate signal unless this line circuit is energized.

Another feature of my invention resides in the means for the control ofthe approach signal in the rear of the first intermediate signal. Inaccordance with this feature of my invention, I supply to the rails oftheintermediate section, at the location of the first intermediatesignal, coded current of a character to which theacutsection apparatusis nonresponsive, such as current of reverse polarity, for example, whena train governed by the first intermediate signal occupies either theintermediate track section or the second end section. I also provide anadditional track relay selectively responsive to current of reversepolarity'at each end of the intermediate track section. One of thesetrack relays controls train detecting means for gov+ erning the supplyofcoded track circuit energy to the rails of the first end section for thecontrol of the'approach signal at its remote end,

while the other traclg'relay s r es to r store the 4 track circuitapparatus to normal when the second end section is vacated.

I shall now describe one form of apparatus embodying my invention andshall then point out the novel features thereof in claims.

In the accompanying drawings, Figs. 1 and 2 taken together illustratethecircuits and apparatus for the'control of a pair ofopposing intermediatesignals in a signaling system of the type shown in the Van Horn patentreferred to, for use in placeof that shown in Fig. 1c of the patent.More particularly, the apparatus of Fig. 1 is for use at the signallocation E of Fig. is of the patent, and that of Fig. 2 is for use atthe cut section location F. As shown, Fig. 2 shows back contact codingcut section apparatus, the.operation of which corresponds to thealternative form provided for use at location E p by Van Horn and shownin his Fig. 5.

Similar reference characters refer to similar parts in both views, andthe local sources of current for energizing the various local circuits.are identified in the usual manner by the reference characters B and C.Furthermore, reference characters similar to those of the Van Hornpatent have been used to identify each of the relays which has acounterpart in the Van Horn patent. Van Horns signal 'lW has beenreplaced by a signal 9W at location F, Fig. 2, which is governed by apolar neutral relay SHDRcontrolled over line wires 2| and Why the codedetector relay II-IR/at location E. To meet the requirements of aparticular railroad, Van Horns position light signals have been replacedby color light signals and an auxiliary motor car indicator systemprovided for warning the operators of hand cars or the like of theapproach of trains.

The motor car indicators, not shown, are coning'system. Although themotor car indicator system forms no part of my invention, theserepeating relays are shown because they are used to provide approachlighting for the signals.

Each of the track relays shown herein is of the biased polar type asindicated'conven'tionallyby an arrow on the relay winding, each suchrelay being responsive to current of the polarity supplied by thebattery at the remote end of its section, but'not to current from theadjacent track battery.

The circuits of Fig. 1 for supplying energy to the rails of section (RThave been modified in accordance with my invention by includingcontactsof a pole changer relay 'I'IPC therein, and also the winding ofatrack relay AETR. respon sive to current of the opposite polarity-tothat which track relay TEIR is responsive. Relay AETR controls aslow'release repeating relay AETP. A similar track-relay AWTR andrepeating relay AW'I'P are included in :the circuits of Fig. 2. RelayI'IPC is normally energized and is released only when an eastbound trainis oc curving section'E-J'; Y I The track circuit system as shown is inits normal inactive condition as set up. forwest. bound traffic, withthe westbound traffic control relay SWFSR energized and the eastboundtrafilc control relay BEFSR released, and with the signal control relaysBRHSRand IULHSR released, so that relay lULTC'IM:= which it is t m- 1,under,

stood, is controlled as shown in Fig. lcl of the Van Horn patent, issteadily energized and is supplying current from the battery IS to therails of section IOLT. In Fig. 2, the track relay BETR and its slowrelease repeating relay SETFSA are steadily energized. The transmitterrelay BWCTM is energized over front contact 196. of relay SETFSA, itscircuit extending to terminal B at back contact I95 of a relay SOD, andis supplying steady current to the rails of section 'IRT. Relay 9CD is acode detector relay which replaces the relays ETBSA and WTBSA of VanHorns Fig. 5. w

In Fig. 1, the track relay 'IETR, and its slow release repeating relay'IETFSA are steadily energized, and the code transmitter relay lWCTM isenergized over contacts 69- 63, as in the Van Horn patent, and issupplying current to the rails of section BRT so that relays BRTR and@RTFSA are steadily energized.

Assuming now that the operator energizes relay IULHSR to set the systeminto operation and to clear the signal for westbound traffic, relayIOLHSR will open the circuit for relay IULTCTM and the energized relaysabove described will release in cascade, and relay GRTFSA upon releasingwill connect relay BRTCTM either to terminal IBOB or to terminal 75B ofa suitable source of coded current, depending upon whether or not signal6L has been cleared to cause relay BRTCTM to supply coded current to therails of section BRT, as explained in the Van Horn patent.

In Fig. l, the first impulse of coded current picks up relays 'IWTR and'IWTFSA, and relay 'IECTM is energized over back contacts 69, 68 and 16and front contact 13 to supply current to the rails of section lRT sothat in Fig. 2, relays QWTR and SWTFSA pick up and relay SECTM isenergized to supply current to the rails of section IGL'I' so thatrelays IBLTR and IULTFSA pick up. At the end of the first code impulsereceived by relay TWTR, a code detector relay 1CD, which replaces VanHorn's relay IBSA, picks up over back contact I18 and front contact I19and a back contact of relay 'IETFSA and completes a circuit for theprimary winding of the decoding transformerDT. The current supplied totransformer DT is periodically reversed in polarity by the codeoperation of a contact of relay 'IWTR in this circuit, causingalternating current of the code frequency to be induced in its secondarywinding. This alternating current is rectified by contact I80 of relay'IWTR so that the signal relay 'IHR becomes energized. Relay II-IRresponds to either '75 or 180 code, and governs the stop and cautionaspects of signal TE... The proceed aspect of signal (E isgoverned by asignalrelay IDR which is selectively energized through a resonantdecoding unit, IBBDU when transformer HT is supplied with 180 code.

When relay II-IR picks up, the directional stick relay 'IWS is energizedover contacts H1, H and 12, and-.the opening of back contacts 68 and16in the circuit for relay lECTMcauses it to release, so that .in Fig.2, relaySWTR releases and picksup relay 9CD. The signal rea circuit forrelay lECTM which extends over back contact 69, front contacts 68 and 61toterminal B at back contact 60.

Two code transmitters T and IBDCT of the pendulum type, which closetheir contacts 75 and times per minute respectively, are set intooperation by the energization of relay TWS, and the periodic operationof contact 61 causes relay -IECTM to supply 180 code to the rails ofsection 'IRT to operate relay BWTR,

The continued code operation of relay BWTR maintains relays QWTFSA and9CD picked up, and the periodic closing of its back contact causes relayBECTM to supply 180 code to relay IDLTR which code is opposite in phaseto that supplied to relay SWTR. The purpose of this back contact codingis to provide compensation when the on and off periods of the code arenot equal, due to over-energization or under-energization of the trackcircuits.

The head block signal IBLA will now display a proceed indication, forreasons explained in the Van Horn patent.

It will now be assumed that a westbound train governed by signal IULApasses through the block. When the train enters the switch section ET,the track relay 9TB releases and picks up a directional stick relaylllLSRover a contact closed by signal [OLA in its energized position.Relay IOLSR is held energized over a stick circuit following the returnof the signal to stop, until the train vacates sections 9T and lcLT andcoded current is received over the rails of section lOLT. When the trainenters section IGLT, and shunts the track relay I ULTR,

relay IGLTFSA will release, disconnectingtera minal B from line wire 25so that relay SETPR. will release to complete the lighting circuit forsignal 9W, energizing lamp G or Y to cause the signal to indicateproceed or caution, depending upon whether relay SHDR is energizedby-current of normal or reverse polarity. Current of normal polarity issupplied to relay,

SHDR only when sections DE and E-F are supplied with 180 code and relayIDR occupies its energized position.

When the Westbound train referred toenters section 'lRT, the track relayQWTR is shunted, releasing relays SWTFSA, 9CD, 9HDR and QECTM. Lamps Gand Y of signal 9W are dark and lamp R is lighted to indicate stop, dueto the release of relay SHDR by relays QWTFSA and 9CD. The seriesconnected relay SHDP also releases and shifts the circuit for relayIECTM from contact 61 to contact 15 so that 75 code is supplied to therails of section lRT in front of the train.

The purpose of this 15 code connection is to enable relays 9CD and SHDPto be picked up, so as to cause the circuit for supplying 180 code tosectionlRT'to be re-established, in the event the train vacates sectionlRT without occupying the advance section ERT.

Assuming however, that the westbound train enters section BRT, relayTWTR will be shunted.

and will release relays 'IWTFS A, 1CD,-1HR and 113R... Relay lWTESAreleases relay TWIPR to lay SHDR in Fig' 2 now picks up over front "P-,.fi-?q lea s its front man amass light lamp R of signal 13, and completes astick circuit for relay 1W6 over contacts 13 and 14 the? r lay ,le pcked When the westbound train vacates section IRT, relay IECTM is. setinto operation over the circuit including back contacts 59 and 68, frontcontacts 16 and I5 and back contact 60 tcsnpplr T reds iothe r ilsattention lB'r.

which code is repeated by the cut section apparatus-of Fig. 2 into'the'rails of section 'lQLT.

Ordinarily the signal control relay 'for signal liiLAis released as-soonas the train passes the signal, but if relay ltLHSR is now energized,this signal will indicatecaution. Otherwise the system will return toits inactive condition in themanner explained in the Van Horn patent,the reception of coded current at point G by relay lilLTR releasingrelay IULSR and causing relay liiLTCTM to become energizedto supplysteady current to the rails of section HJLT, in which case relay QETRwill pick up during the periods when relay QECTM is; released. Sincetheseare the periods during which relay QWTR is'pioked up, the circuit'for relay QWTFSA will beheldo'pen substantially continuously and thisrelay will release and-open the circuits for relays SECTM and 90D. RelayQETR will thereupon become steadily energized, and relay 9CDwill'release. Relay QETESA will pick up, following the release of relayQWTFSA, during a code interval when relay QWTR is released, and thenrelay SWCTM will pick up over back contact 195 and front contact I96 tohold relay QWTR. released and to supply steady current to the rails ofsection 'IRT.

In Fig. 1, relay 'IETR will be picked up by the current supplied byrelay BWCTM during an interval between the code impulses supplied byrelay TECTM so that relay TETFSA will pick up and open its back contact60. This will hold relay IECTM released, enabling relays TETR andlETFSA-tobecome steadily energized.

When the westbound train above referred to vacates the block, the codeoperation of relay GRfICTM'and of relay lWTR is resumed. Relay 'IWTFSApicks up in response to the first code impulse received by relay 'IWTRbut since relay 'IETFSA' isalso energized, relays 101) and IHR remainreleased, and relay lWS is released by the opening 'of the back contact13 of relay 'IWTFSA. Relay 'IWCTM then becomes steadily energized overthe circuit including back contacts 63, 62, 6! and front contact 60, tosupply steady current to section BRT. The apparatus is now in its normalcondition as shown in the drawings.

Itwill be seen from the foregoing that the control limits for the signalin approach to signal 9W extend to point E and have not been shortenedby the removal of the westbound signal from point E to point F, and thatthe control limits for signal 9W include section EF, due to the controlof the signal relay SHDR by the code detector relay 9CD for thatsection.

The operation of the system when set up for eastbound traffic movementswill now be described. These operations are generally similar to thosealready described except for those opr' erations which involve trainmovements through section I t In the normal inactive condition foreastbound train movements, the eastbound traffic. control relay 8EFSR isenergized and the westbound traffic control relay SWFSR is released, andthe cascade connected relays which'are' energized-are,

the relays I-BRTCTM, "iw ra f i'wrrse, lE CTM, SWT-R, awrFsaeEUr-M,learn and scrapes.

When the signal-control relayfiBHSR isenere gized by thebperator toset'the system intooper tqtti mibal 460B or filit a fa suitable scurce'cr 8 r. l coded -'ciiirent; depending upon "whether or in'ot' signal 10Rhas been clea'red, and relay l-OLTCTM is caused to supply '75 or 180code to the rails of section .IBILT. Inresponse to this code relay QETR.energizes relays 9ETF SA and BCD, and supplies coded impulses over itsback contactto relay QWCTM which repeats them'into section 'IR'I.

In Fig. 1-, relay 'lETR is set'into operation to energize relays1ETFSA,-1CD and THE, and if 180 code is being received, to also energizerelay 'IDR. Relay *IHR energizes the directional "stick relay IE8, andrelay TES sets the code transmitters 150T and I80CT into operation.Relay 'IETPR is now energized by relay IETFSA, and relay 'IWCTM issupplied with 180 coded current over the circuit including backcontact63 and frontcontactsfiz and l l 2, a front-contac'tof relay'IETPR and back contact 13, and supplies 180 code to section BRT. l

' The response of relay BRTR. to this code causes When the train entersthe switch section 5T, the

track relay 5TB releases and picks up the directional stick-relay BRSRover a contact closed by signal ERA in its energized position. RelayGRSR is held energized over a stick circuit following the return of thesignal to stop until the train vacates sections ET and GET and codedcurrent is received over the rails of section GRT. When the train enterssection BRT and shunts the track relay BRTR; relay fiRTFSA will release,disconnecting terminal B from line Wire 23 so that relay 'IWTPR willrelease to complete thelighting circuit for signal 7E, energizing lamp Gor Y to cause the signal to indicate proceed or caution depending uponwhether relay IDR' is energized or not.

When this eastbound train enters section IRT,

the track relay 'IETR is shunted, releasing relays 'IETFSA, 10D and IHR,and also releasing relay FDR if energized, so that lamp R of signal 1Ebecomes lighted in place of lamp G or Y.

The release of relay 'IETFSA releases relay IETPR which opens thecircuit for relay IWCTM and stops the delivery of coded current to therails of section ElRT, Theclosing of back contact 60 of relay IE'IFSAcompletesthe stick ciredit for relay'lES to maintainthat relay pickedup, but relay 'ITPC now releases, since as shown by the drawing, thisrelay is controllable-by relays AETP and 'IETFSA when relay IE8 ispicked up.

The release of relay 'ITPC reverses the connections of the track batteryfor supplying current to the rails of section 'IRT at its left-hand endand at the sametime'completes a circuit for relay JECTM which includesfront contact 69 of relay' lES, back contacts of relays AETP'and ITPC,contact 61 of the code transmitter JBOCT and back contact Ell of relay'IETFSA.

Relay IEC'IM now supplies coded current of reverse polarity totherails-of section (RT at its "entrance end. When the eastbound trainpasses from -section 1R1 into section! @LT',relay fiETR' is-sh ited andreIayQWGTM-is held de-.

ener ized; Relays sET-risA and SE'TPRQrelease; lighting lamp-Rof the opos ng Si nal aw.

When-the eastbound train yacates' section'lRT, relay AWTR responds inplace of relay QWTR, andfthe 180 code now being supplied to section 'RrTis not repeated into section IDLTnpf-is this.

a teflectiiie tocentral signal svnuuie AW'I'P which connects terminal Bto line wire 24, thereby energizing relay 'IETPR to complete a circuitfor relay IWCTM over back contacts 63 and 62, front contact 6|, acontact of the code transmitter 150T, a front contact of relay TETPR andextending to terminal B at back contact '3.

Relay TWCTM therefore supplies 15 code to section GRT enabling signal6RA to display a caution indication when section IRT is vacated,provided the operator has reenergized its control relay as explained inthe Van Horn patent. It will be seen that in this case the unoccupiedcondition of section GRT is detected by the 75 code supplied to thatsection, and the unoccupied condition of section 'IRT is detected by thecoded current of reverse polarity supplied at point E and received overthe track rails at point F, by the track relay AWTR.

The directional stick relay GRSR releases when coded current is receivedover the rails of section GR'I, and if the operator has not reenergizedthe control relay for signal BRA, the apparatus at that location willhave assumed its inactive condition and relay SRTCTM will now beenergized to supply steady current to the rails of section BRT asexplained in the Van Horn patent. Relay 'IWTR will be picked up by thecurrent supplied by relay BRTC'IM during an interval between the codeimpulses supplied by relay 'IWCTM so that relay 'IWTFSA will pick up andopen its back contact 13. This will hold relay TWCTM released, enablingrelays 'IWTR and 'IWTFSA to become steadily energized. Relay 'IWTPR willbe picked up by relay GRIFSA or relay TWTFSA to open the lightingcircuit for signal 1E.

When the eastbound train vacates the block, 75 code is supplied tosection I LT and relay QE'IR resumes its code operation. Relays QETFSAand 9CD pick up, and relay BETPR is energized to open the lightingcircuit for signal 9W. Since relays SWTR and QWTF'SA are now released,relay QWCTM is set into operation to repeat the 75 code received fromsection IOL'I with a reversal of phase, into section 'IRT, which sectionis also being supplied with 180 code of reverse polarity by relay IECTM.The current supplied by relay SWCTM will be eilective, during theintervals when relay "IECTM is released,

to energize relay AETR in place of relay IETR,

due to the reversal of the connections to these relays, relay 'ITPC nowbeing in its released position. Relay AETR will therefore pick up, atleast momentarily, and will energize its slow release repeating relayAETP, which in-turn, energizes relay 'ITPC thereby opening the circuitfor relay IECTM to prevent further transmission of 180 code impulses ofreverse polarity. and in addition, rendering relay 'IETR responsive tothe 75 code impulses supplied by relay BWCTM in place of relay AETR.Relay IETR therefore picks up relay IETFSA which maintains relay 'ITPCpicked up, and relay AETP releases, along with relays AWTR and AW'IP ofFig. 2.

If the operator has already reenergized the control relay for signal 6RAso as to maintain the system in operation, relay IWCTM at this time willbe supplying 75 code to section 6RT and relays 'IWTR and 'IWTFSA will bereleased. In this case, when relay 'IETR resumes its '75 code operationrelays 1CD and THE will pick up and relay IE TPR will be held energizedby relay 7ETFsA,- 'and;. relay 'IWC'IM .Will supply 18( code 10 tosection SRT due to the closing of that branch of its circuit whichincludes front contact 62 of relay 'IHR and contact H2 of the codetransmitter IBUCT.

If the apparatus at the location of signal 6RA has been restored to itsnormal inactive condition so that steady current is being supplied tosection GRT, relay IW'IFSA will be in its energized position, preventingthe energization of relays PCB and II-IR when relay IETFSA picks up. Inthis case relay 'IES will be released by the opening of back contact 60,and will complete a circuit for relay 'IECTM over back contacts 69, 68and 16 and front contact 13 so that relay 'IECTM will supply steadycurrent to section 'IRT. In Fig. 2 this steady current will over-ridethe code and effect the reversal of the cut section apparatus in themanner already described for the opposite direction of traffic movement,to cause steady current to be supplied to section IOLT and therebyenergize relays I ULTR and IULTFSA to stop the code operation of relay IUL'ICTM. The apparatus will then be in its inactive condition for theeast bound trafic direction, corresponding to the inactive condition forthe westbound direction shown.

It will be seen from the foregoing that when the eastbound direction isset up, the control limits for the signal in approach to signal IEextend to point F to reach the location of the opposing signal 1W, butwithout shortening the control limits for signal 1E.

Although I have herein shown and described only one form of apparatusembodying my invention, it is understood that various changes andmodifications may be made therein within the scope of the appendedclaims without departing from the spirit and scope of my invention.

Having thus described my invention, what I claim is:

1. In a signaling system for a stretch of single track railroadcomprising a first and a second end section and an intermediate section,said sections being equipped with cascade connected coded track circuitsarranged to be supplied with coded currents of a first or a secondcharacter at either end of the stretch, said coded track circuitscontrolling a first and a second intermediate signal for governing trainmovements in opposite directions through the intermediate section andalso controlling approach signals at the ends of the stretch forgoverning train movements into the stretch, each signal being adapted toindicate proceed or caution depending upon whether the coded currentwhich controls it is of said first or second character, the combinationof decoding means and of directional relays for two directionscontrolled bythe track circuits for the first end section and theintermediate section, means controlled by said directional relaysefifective when a given traflic direction is set up for rendering thedecoding means responsive to the coded currents supplied. over the railsof the second end section and intermediate section in cascade and forenabling said decoding means to energize the first intermediate signalin accordance with the character of said coded current and to alsosupply coded current of said first character to the rails of the firstend section to enable its approach signal to display a proceed aspect,means for supplying train detecting current of a third distinctivecharacter to the rails of saidintermediate section only, whenever atrain governed by the first intermediate signal passes through suchsection, a" track relay :selectively'responsive to the current of saidthird distinctive character received over thelrails .of the,intermediate section when vacated by said train, means ccntrolledby saidtrackrelay when energized for supplying coded current of said secondcharacter to the rails of said first end section .to cause the approachsignal at the end -.of such section to display its caution aspect,

:means for terminating the supply of current of said third distinctivecharacter when coded current is again received over the rails of saidsecond endsection, means controlled by said directional relays effectivewhen the opposite traffic directionis setup for energizing said.decoding means if coded current is being supplied .over the rails ofsaid first end section, and for causing said decoding means to supplycoded current of .said first or second. character, depending uponWhether -or not it is energized, to the rails of the intermediatesectionand second end section in cascade for the control of the approachsignalat the re- :mote end of said second end section, and line circuitmeans rendered effective when said current supplied'by said decodingmeans is received at the oppositeend of said intermediate section 'forenergizing the second intermediate signal to cause such signal todisplay its caution or proceed aspect dependent upon the condition ofsaid decoding means. i

'2. In combination with a stretch of railway track comprising a firstanda second end secj-tion and anyintermediate section equipped with cascadeconnected coded track circuits, and having an intermediate signal forgoverning traiiic movements into the intermediate section from saidfirst ,end section and an approach signal for governing tramc movementsin the same direction into said first end section, means for sup-:plying' coded currents of a first or second frequency to the rails ofthe second end section'at one end of the stretch for the control ,ofsaid intermediate signal :and-for the control ,of said approach signal,decoding means at the intermediate signal location adapted to cause theintermediate signal to display a caution or proceed aspect when codedcurrent of said first or second frequency-is received over the rails .ofthecascade connected intermediate and second end sections and to alsosupply coded current of the second 'frequency to the rails of the firstsection to cause the approach signal to display its proceed aspect,means for supplying train detecting current of a distinctive characterto the rails of the intermediate section only, whenever a train governedby said intermediate signal passes through such section, meansselectively respon sive to the current of said distinctive characterreceived over the rails of the intermediate section when vacated by thetrain for supplying coded currentof the first frequency to the rails ofthe said first end section to cause the 'approach signal ;to;display itscaution aspect, and means for terminating the supply of current of saiddistinctive characteras soon as the train vacates the second endsectionla'nd coded current is again received over the'rails of suchsection and issupplied at the adjoining end to the'rails of theintermediate section. V

3. In combination with a stretch of railway trackicomprising a first anda second end section and an intermediate section equipped with cascadeconnectedcoded track circuits, and having an intermediate signal forgoverning traffic kmovements into the intermediate section fromto'supply coded current of the second frequency,

to the rails of the cascade connected intermediate and second endsections to .cause the approach signal to display its proceed aspectwhen coded current of said first .or second frequency. is received overtherails of said first end .section, code detecting means at theintermediate signal location selectively'responsive Ito coded currentreceived over the rails of said intermediate section, a signal relay forcontrolling said intermediate. signal, a circuit for controlling saidsignal relay which is closed only when said code detecting means isenergizedto cause the intermediate signal to display a caution orproceed aspect depending upon whether said decoding means is respondingto-coded current of said first or second frequency, means for detectingwhen saidsignal relay circuit is closed comprising a series connectedrelay in' said circuit at the location of said decoding means, and meanscontrolled'by said series connected relay forzpreventing the decodingmeans from supplying coded current of the second frequency to the railsexcept when the circuit-for said signal relay is energized.

4. In a reversible track circuit system for an intermediate section inastretch of railway track, said section having a' transmitter relay ateach end which is supplied at times with impulses of coded current inaccordance with traffic conditions in an adjoining section in saidstretch, and having a source of current and a firstbiased polar trackrelay'at each ,end connected in series 'to the track rails over contactsof the associated transmitter relay in suchmanner that when such relayis supplied with coded current its contacts .said section which isconnected to the track rails over a contact of theassoc'iated'transmitter relay closed only when the adjacent source is ldisconnected, each second track relay being responsive only to currentof reverse polarity supplied thereto by the source at the opposite end--when said pole changer contacts are reversed,

mal in response to the energization of the second track relay at said 7.one end. when current of 13 reverse polarity is supplied thereto overthe rails of said section, signaling means controlled by each firsttrack relay for indicating the unoccupied condition of said section whensuch relay is supplied with impulses of normal polarity over the railsof said section, train detecting means for indicating when such sectionis vacated by a train, and means for energizing said train detectingmeans in response to the energization of the second track relay at theopposite end of the stretch when current of reverse polarity is suppliedthereto :from the source at the location of said pole changer contacts.

5. In a reversible track circuit system for an intermediate section in astretch of railway track, said section having a transmitter relay ateach end which is supplied at times with impulses of coded current, andhaving a source of current and a first biased polar track relay at eachend connected in series to the track rails over contacts of theassociated transmitter relay in such manner that when such relay issupplied with coded current its contacts periodically disconnect theadjacent source from the track rails without disconnecting the trackrelay, each such track relay being responsive to current of the polaritynormally supplied at the opposite end but not to current of the polaritynormally supplied to the rails at the adjacent end of said section,means governed by each first track relay for supplying impulses of codedcurrent to the rails of an adjoining section in said stretch, suchadjoining section having means for operating the transmitter relayassociated with such track relay to supply impulses of coded current tothe rails of said intermediate section, the combina-- tion of theforegoing with normally inactive pole changer contacts in the circuitconnecting the track relay and source to the rails at a first end ofsaid intermediate section, a second biased polar track relay at each endof such section which is connected to the track rails over a contact ofthe associated transmitter relay closed only when the adjacent source isdisconnected, each second track relay being responsive only to currentof reverse polarity supplied thereto from the opposite end when saidpole changer contacts are reversed, means controlled by the first trackrelay at said first end of the intermediate section for causing saidpole changer contacts to assume their reverse position when a trainenters said intermediate section from an adjoining section at said firstend, means for periodically operating the transmitter relay associatedwith said first track relay to supply coded current of reverse polarityto the rails at the first end of the section, eifective whenever saidpole changer contacts are reversed, means for restoring said polechanger contacts to normal in response to the energization of the secondtrack relay at said first end when current of reverse polarity issupplied thereto over the rails of said intermediate section, traindetecting means for indicating when said intermediate section is vacatedby a train, and means for operating said train detecting means inresponse to the energization of the second track relay at the second endof such section when current of reverse polarity is supplied theretofrom the source at the location of said pole changer contacts.

REED B. ANNEAR.

No references cited.

